This disclosure relates to drilling fluids with leakoff control, and methods of drilling a wellbore with the drilling fluids.
A drilling fluid, also called drilling mud, is a complex heterogeneous fluid. It can facilitate drilling operations by lubricating and cooling the bit, carrying drill cuttings to the surface, and providing buoyancy to support drill pipe and casing. The drilling fluid also provides hydrostatic pressure to prevent collapse of unstable strata and intrusion of undesirable fluid flow from the formation.
Drilling fluids are typically classified according to their base fluid. In water-based muds, solid particles are suspended in fresh water or brine. If present, oil can be emulsified in the water. Nonetheless, the water is the continuous phase. Oil-based muds (OBM) are the opposite or inverse. Solid particles are suspended in oil, and water or brine is emulsified in the oil and therefore the oil is the continuous phase.
Since oil is much more expensive than water, water-based drilling fluids are more economical than oil-based drilling fluids. However, water-based drilling fluids are the least efficient means of transporting the drill cuttings to the surface. During the drilling of the well, and especially in the drilling of horizontal laterals, the need to efficiently remove the drill cuttings is important to the well. Gravity effects during the drilling of high angle and horizontal wells cause cuttings to fall to the bottom of the drilled hole along what is termed the cuttings bed. The cleanup and removal of the formation cuttings are always of concern during the drilling process since drilling fluids are often less than perfect particle transport mediums. The inability of cuttings removal can have detrimental effects on the drilling processes, and can even stick the drill pipe if the cuttings bed buildup becomes too severe.
Despite all the advances, the art would be receptive to alternative methods that are effective to improve cuttings removal efficiencies for drilling fluids, particularly water-based drilling fluids. It would be a further advantage if such methods are effective to eliminate or reduce fluid leakoff.